EP-PS No. 592,242 describes methods and compositions for a completely novel fibrin sealant involving contacting a desired site with a composition comprising fibrin monomer and converting this monomer to a fibrin polymer concurrently with the contacting step. The term "fibrin" is defined as fibrin I, fibrin II, and/or des .beta..beta. fibrin.
Further a method is known from EP 0 654 669 for separating a component, such as fibrin monomer from blood. This method for separating the components of a liquid containing several components of a varying specific gravities involves the steps of the blood being collected in a first chamber of a device, said chamber being defined by a substantially axially symmetrical outer and inner wall. The blood is subjected to a centrifugation by way of rotation of the device about the axis of symmetry of the chamber so as to establish a concentric interface between the components of the blood. At least one of the components of the blood such as plasma is subsequently transferred to a second chamber in the device preferably by way of reduction of the volume of the first chamber during a continued centrifugation of the device. The substantially axially symmetrical inner wall is provided in the first chamber so as to ensure that all the blood is subjected to a centrifugal rotation necessary for the separation. This inner wall is of a radius adapted to the desired speed of rotation.
In the second chamber a fraction with non-crosslinked fibrin polymer is separated from the plasma by means of a suitable enzyme and subsequently redissolved into fibrin monomer and transferred to a syringe through a filter by reducing the volume of the second chamber.
It turned out, however, that the separation of a component, such as fibrin monomer from blood, only by way of filtration in a device of the above type does not provide a satisfying result. This is mainly due to the fact that it is difficult to ensure a satisfying separation of the fraction containing fibrin monomer in the second chamber, and accordingly a relatively high amount of the content in the blood of fibrin is lost during the following transfer of a fluid fraction from the second chamber to the first chamber during the succeeding step of the method.
Also, in the earlier fibrin monomer method, the above-described treatment of fibrinogen within the plasma with a suitable enzyme produced the non-crosslinked fibrin polymer in the form of a thick gel mass at the bottom of the second chamber. To provide the desired fibrin monomer solution, a significant amount of redissolving buffer combined with substantial agitation was required. This resulted in several drawbacks. First, preferred fibrin monomer methods, e.g., for use as a fibrin sealant as in EP 592,242, require concentrated fibrin monomer solutions, and the large amount of redissolving buffer or solvent required to dissolve the gel mass provided dilute solutions which do not work as well. Further, the substantial agitation required to dissolve the gel mass into a fibrin monomer solution can cause damage to the device and to the fibrin itself.
A co-pending application entitled "Method and Device for Separating a Component Such as Fibrin I From Blood Plasma", issued as U.S. Pat. No. 5,824,230 discloses an invention including a method which provides for the separation of non-crosslinked fibrin polymer from a plasma fraction in a cylindrical chamber carried out during centrifugation whereby the non-crosslinked fibrin polymer is deposited on the outer wall of the chamber, whereafter the remaining fluid fraction collected in the chamber is removed from the chamber, and that the fraction with non-crosslinked fibrin polymer remaining in the chamber substantially deposited on the wall is caused to be dissolved by addition of a solvent and by centrifugal agitation.
Since the treatment of the plasma with the enzyme is carried out during continued centrifugation, the centrifugal force upon the resulting non-crosslinked fibrin polymer provides that it is precipitated as a thin gel film which substantially sticks to the circumferential walls of the chamber. The remaining plasma liquid deposits at the bottom of the chamber when the centrifugation is stopped and can be removed by any convenient means. The desired fibrin monomer solution is thereafter provided by introducing a suitable redissolving buffer solution into the chamber and subjecting the buffer in the gel-coated chamber to centrifugal agitation. This method provides advantages over prior methods. First, the redissolving of the non-crosslinked gel by the buffer solution is extremely efficient due in part to the large surface area of the same volume of fibrin gel compared to the fibrin gel mass provided in prior methods. Accordingly, the gel can be dissolved with small amounts of redissolving buffer resulting in a desirably concentrated fibrin monomer solution. Further, the action of the centrifugal agitation on the buffer solution within the gel-coated chamber is a comparatively gentle method causing no damage to the equipment or to the fibrin monomer product. The resulting high concentration fibrin monomer solution is in the range of 10-30 mg of fibrin monomer per ml of solution and preferably about 25 mg/ml.
The copending invention also includes a method involving feeding of blood preferably in the presence of an anticoagulant to a first annular chamber in a device, where the annular chamber is defined by a cylindrical outer wall and a cylindrical inner wall, both walls extending coaxially about a common axis, as well as by a top wall and a bottom wall, where the top wall or the bottom wall is formed by a piston body displaceable within the first chamber, said method further involving a centrifugation of the device about the said common axis to substantially separate blood into a cell fraction and a plasma fraction followed by the resulting plasma fraction being transferred while influenced by the piston body to a second chamber defined by an outer cylindrical wall, which extends coaxially with said common axis, whereby a fraction with non-crosslinked fibrin polymer is caused to be separated in the second chamber while a suitable enzyme is being added. This method is characterized in that the fibrinogen-containing plasma fraction is subjected to the enzyme during centrifugation so that the resulting non-crosslinked fibrin polymer is deposited on the cylindrical outer wall of said second chamber, whereafter the fluid fraction collected at the bottom of the second chamber is transferred while influenced by the piston body to the first chamber, and that the fraction with non-crosslinked fibrin polymer remaining in the second chamber substantially deposited on the cylindrical wall is caused to be dissolved by addition of a solvent and by centrifugal agitation. Thereafter the enzyme can be removed, if desired, and the so-produced fibrin monomer solution is transferred to any desired receiving container.
Accordingly, an aseptic condition for collecting the solution is easily maintained. After the fibrin monomer has been redissolved, it can be transferred to a receiving container, such as a syringe for further use as described in the prior art. Before the transfer, the enzyme can be removed by any convenient means.
The above copending application further discloses a device for separating components from a liquid by way of centrifugation about a central axis of rotation comprises a first annular chamber defined by an outer cylindrical wall and an inner cylindrical wall, both walls being concentrically accommodated about said axis of rotation, as well as by a top wall and a bottom wall, where the bottom wall is formed by a piston body displaceable within said first chamber, said device further comprising a second chamber communicating with the first chamber through a first conduit and being defined by an outer cylindrical wall concentrically accommodated about the axis of rotation and by said piston body and a bottom wall, where said second chamber is adapted to be positioned below the first chamber during the centrifugation, and where said device also comprises blood feeding means for feeding blood to the first chamber and composition feeding means for feeding composition promoting the separation as well as receiving means for the connection of at least one liquid-receiving container, where the receiving means communicate with the second chamber through a second conduit. In a preferred embodiment, the piston rod comprises the inner wall of the first chamber.
This inventive device for carrying out the method according to the copending invention is characterized in that the first conduit comprises at least one channel extending between an opening at the top wall of the first chamber and an opening at the bottom wall of the second chamber.
As a result a device is provided which is relatively simple and which independent of the position of the piston ensures an easy and fast transfer of the fractions in question from one chamber to the other chamber, and especially of the fluid fraction from the second chamber to the first chamber after the separation of the fibrin-l-containing fraction. The latter is especially due to the fact that the fluid is automatically concentrated at the bottom of the second chamber when the centrifugation is stopped, whereby it can be easily transferred to the first chamber by the piston being moved.
According to the copending invention it is particularly preferred that said at least one channel extends through the interior of the outer cylindrical wall in both the first and the second chamber with the result that the device is particularly simple and easy to manufacture.
Further, the opening of the channel at the bottom wall of the second chamber may be centrally accommodated in the chamber in connection with a recess formed by the bottom wall. As a result, the fluid fraction in question is easily and quickly guided directly to the inlet opening of the channel. Alternatively, each channel may be formed by a pipe extending rectilinearly through the piston body and being secured at the ends in the top wall of the first chamber and the bottom wall, respectively, of the second chamber where it communicates with channel portions ending in the respective chamber.
Additionally, the first and the second chamber may in a particularly simple manner comprise a common outer cylindrical wall shaped by an outer and an inner cylinder sealingly fitting within one another and defining therebetween an axially extending channel, and the cylinders may be terminated at one end by an end wall comprising an opening allowing passage of a piston rod connected to the piston body, said piston body forming the bottom wall of the first chamber and separating said first chamber from the second chamber, and where the channel extends between the end walls of the cylinders to an opening immediately adjacent the piston rod.
In using such a device and method, suitable reagents for facilitating the separation and treatment of desired components within the blood plasma were preloaded into the second chamber. For example, EP 592,242 describes that the biotin-avidin capture system can be conveniently used to remove the batroxobin from the desired solution. It is required that the biotin batroxobin be present in the second chamber to react with the fibrinogen within the plasma and convert it to a fibrin monomer (which immediately converts to a fibrin polymer). In order to thereafter capture the biotinylated batroxobin using the biotin-avidin system, avidin which is bound, for example, to agarose must also be present in the second chamber. In a closed, automated centrifuge device, these agents need to be loaded into the device prior to blood processing. Preloading of the biotinylated batroxobin and avidin agarose into the same chamber has provided difficulties since the high affinity of the avidin for the biotin, which is relied upon for enzyme capture, prevents sufficient quantities of the enzyme from first reacting with the fibrinogen as is required.